Air dryer module

ABSTRACT

Abstract of the Disclosure 
         
   An air dryer and reservoir assembly for providing compressed air from an air compressor (20) on a heavy motor vehicle which includes an air dryer (14) connected to receive compressed air from the air compressor (20) and a secondary reservoir (12), including an integral purge volume (34), for storing compressed air which passes through the air dryer (14), with the air dryer (14) and the secondary reservoir (12) being securely attached to a housing (16) to form an air dryer reservoir module (10). A primary reservoir (18) for storing compressed air from the air dryer (14) is located remote from the air dryer reservoir module (10). A pressure equalizing mechanism (57) is disposed between the primary reservoir (18) and the secondary reservoir (12) for keeping pressure in the two reservoirs (12,18) equal. Components located within the housing (16) control air flow between the air dryer (14) and the primary and secondary reservoirs (18,12) and also monitor the pneumatic brake system circuits fed by the primary and secondary reservoirs (18,12).

Detailed Description of the Invention Cross Reference to RelatedApplications

[0001] This application is a continuation of U.S. Application No.09/571,897 (Attorney Docket No. 591-97-021) titled "Air Dryer ReservoirModule Components" filed May 16, 2000 and assigned to the assignee ofthe present application, which is a continuation of U.S. patentApplication No. 09/030,583, now U.S. Patent No. 6,074,462, which is acontinuation-in-part of U.S. Patent Application No. 08/993,931, now U.S.Patent No. 5,917,139.

Background of Invention

[0002] This invention relates to air dryers and more particularly to anair dryer and a reservoir, including a separate purge volume,constructed together as a module.

[0003] Air dryers have been used to dry the air in a heavy vehicle airbrake system for many years. The advantages of clean and dry air in airbrake systems has long been recognized, as moisture entrained in the airbrake system may during cold weather operation cause the components ofthe air brake system to freeze, thus rendering the system inoperable.These prior art air dryers normally include a desiccant material throughwhich the compressed air flows. When the vehicle air compressor hascharged the vehicle air reservoirs to a sufficient pressure level, thecompressor is unloaded so that the compressor no longer compresses air.When the compressor is unloaded, a signal is transmitted to a purgevalve carried within the air dryer which causes stored compressed air tobackflow through the desiccant at a controlled rate to regenerate thedesiccant. The air used to regenerate the desiccant can be either fromcompressed air stored in an integral purge volume within the air dryeror from compressed air stored in a separate reservoir.

[0004] Most prior art compressed air systems for heavy vehicle air brakeapplications use three reservoirs which are separate from the air dryer.A compressor feeds compressed air to the air dryer which after flowingthrough the desiccant bed is fed to a remote supply reservoir. Thesupply reservoir is connected to feed compressed air to a primaryreservoir and a secondary reservoir. The primary and secondaryreservoirs feed pneumatic circuits which can control the air brakesystem of the vehicle. For protection from loss of air pressure theprimary and secondary reservoirs each include a check valve in theirpneumatic connections to the supply reservoir. A pneumatic control lineextends from the supply reservoir to an air pressure governor whichcontrols loading and unloading of the air compressor.

Summary of Invention

[0005] The present invention is for an air dryer and reservoir assembly,for providing compressed air from an air compressor for operating thebrakes of a heavy motor vehicle, which includes an air dryer connectedto receive compressed air from the air compressor, a secondary airreservoir separate from the air dryer, a housing containing pneumaticcircuit components for controlling the flow of compressed air from theair compressor through the air dryer to the secondary reservoir havingthe air dryer securely attached to one section thereof and the secondaryreservoir securely attached to another section thereof for securing theair dryer and the secondary reservoir together as a unitary air dryerreservoir module. The compressed air brake system with the air dryerreservoir module also includes a primary air reservoir having apneumatic connection to the housing disposed remote from the secondaryair reservoir with the housing containing pneumatic circuit componentsfor controlling compressed air flow between the air dryer and theprimary air reservoir. Pneumatic circuit protection valves are disposedwithin the housing for monitoring the pneumatic circuits fed by theprimary and secondary reservoirs. A failure detection means is alsodisposed within the housing for detecting a failure of the pneumaticcircuits which are fed by the primary and secondary reservoirs and inthe event of a failure of these pneumatic circuits the speed of theheavy vehicle is limited.

[0006] The herein disclosed air brake system's air charging andtreatment subsystem referred to as the air dryer reservoir moduleprovides for a simplified and cost effective air charging sub-system,using integrated components. The air dryer reservoir module isconfigured in a way that allows the elimination of the supply reservoir,which is used in the standard three reservoir system, while providing ameans of simultaneously sensing both the primary reservoir and thesecondary reservoir for air compressor and air dryer control.

[0007] The air dryer reservoir module integrates components such aspressure protection valves, the air compressor governor, pressure reliefvalves, pressure sensors and the like in a way that eliminates the needfor the supply reservoir, the supply reservoir safety valve, several ofthe standard three reservoir system's external lines and many of itsfittings. The reduction of components, fittings and pneumatic linesreduces potential failure modes. With respect to a standard threereservoir system, the air dryer reservoir module integrates thefollowing components: air dryer, primary and secondary check valves,supply and secondary drain valves, supply reservoir safety valve, thecompressor governor, auxiliary system pressure protection valves, andthe supply and secondary reservoirs.

[0008] A purge volume can be built into the end of the secondaryreservoir to which the air dryer is attached. An internal baffleseparates the secondary reservoir volume from the purge volume. Internalcommunication passages connect the secondary reservoir and purge volumeto the air dryer. The dryer reservoir module can also be constructed toequalize the pressure between the primary reservoir and the secondaryreservoir, such that if the vehicle is parked for a given period of timethe pressure cannot be replenished. Thereby limiting the use of thevehicle with a severely leaking reservoir.

Brief Description of Drawings

[0009] For a better understanding of the invention reference may be hadto the preferred embodiments exemplary of the inventions shown in theaccompanying drawings in which:

[0010]FIG. 1 is an illustration of a prior art three reservoircompressed air charging system;

[0011]FIG. 2 is an illustration of a compressed air charging systemusing an air dryer reservoir module according to the present invention;

[0012]FIG. 2A is an illustration of an inboard view of a portion of thecompressed air charging system using an air dryer reservoir module shownin Figure 2;

[0013]FIG. 3 is a perspective view of an air the present invention;

[0014]FIG. 4 is an illustration of an air dryer reservoir moduleaccording to the present invention showing some of its internalpneumatic flow paths and control components;

[0015]FIG. 5 is an illustration of an air dryer reservoir moduleaccording to the present invention used in a service brake system for aheavy motor vehicle;

[0016]FIG. 6 is a schematic illustration showing the components includedin one embodiment of the air dryer reservoir module; and

[0017]FIG. 6A is a view of an air dryer reservoir module that integratesthe components shown in FIG. 6.

Detailed Description

[0018] Referringnow to the drawings and FIGS. 2 and 3 in particularthere is shown an air dryer reservoir module 10 according to the presentinvention. The air dryer module 10 provides compressed air received froman air compressor 20 for operating the brakes of a heavy motor vehicle.The air dryer module 10 includes an air dryer 14 connected to receivecompressed air from the air compressor 20, a secondary air reservoir 12separate from the air dryer 14, and a housing 16 containing pneumaticcircuit components for controlling the flow of compressed air from theair compressor 20 through the air dryer 14 to the secondary reservoir 12and a primary reservoir 18. The housing 16 has the air dryer 14 securelyattached to one section thereof and the secondary reservoir 12 securelyattached to another section thereof for joining the air dryer 14 and thesecondary reservoir 12 together forming the unitary air dryer reservoirmodule 10. The compressed air brake system with the air dryer reservoirmodule 10 also includes the primary air reservoir 18 having a pneumaticconnection 22 to the housing 16 disposed remote from the secondary airreservoir 12. The housing 16 also containing pneumatic circuitcomponents for controlling compressed air flow between the air dryer 14and the primary air reservoir 18. Pneumatic circuit protection valvesare disposed within the housing 16 for monitoring the pneumatic circuitsfed by the primary reservoir 18 and the secondary reservoir 12. Afailure detection means is also disposed within the housing 16 fordetecting a failure of the pneumatic circuits which are fed by theprimary and secondary reservoirs 18,12 and in the event of a failure ofthese pneumatic circuits the speed of the heavy vehicle is limited.

[0019] Referring to Figure 1 there is shown a relatively standard priorart three reservoir pneumatic charging system for the brake system of aheavy motor vehicle. Most prior art compressed air systems for heavyvehicle air brake applications use a primary reservoir 18, a secondaryreservoir 12 and a supply reservoir 60 which are separate from the airdryer. A compressor 20 feeds compressed air to an air dryer fit whichafter flowing through the desiccant bed is fed to the remote supplyreservoir 60. The supply reservoir 60 is connected to feed compressedair to the primary reservoir 18 and the secondary reservoir 12. Theprimary reservoir 18 and the secondary reservoir 12 feed pneumaticcircuits which can control the air brake system of the vehicle. Forprotection from loss of air pressure the primary and secondaryreservoirs each include a check valve, 66 and 64 respectively, in theirpneumatic connections to the supply reservoir 60. A pneumatic controlline 68 extends from the supply reservoir 60 to an air pressure governor70, mounted on the air compressor 20. which controls loading andunloading of the air compressor 20. The secondary reservoir 12 also hasattached thereto an 85 psi pressure protection valve 72 and a 55 psipressure protection valve 74 which feed accessories on the heavyvehicle. The supply reservoir 60 includes a safety valve 76 which is setfor 150 psi. All three of the reservoirs 12, 18 and 60 include a manualdrain valve which can be used for draining liquid from their respectivereservoir.

[0020] Comparing Figures 1 and 2 illustrates the difference between theair dryer reservoir module 10 and the standard three reservoir system.The air dryer reservoir module 10 integrates components, eliminatespneumatic lines and connections as compared to a standard threereservoir system as shown in Figure 1. The air dryer reservoir module 10which is one of the air brake system's charging sub-systems is intendedfor use on heavy vehicles, such as tractors and trucks, and isconfigured as shown in the Figures 2. and 3. Manufacturing of the airdryer reservoir module 10 system is intended to be by conventionalmethods.

[0021] The air dryer reservoir module is different from prior art inthat it integrates charging system components in a way that eliminatescomponents, pneumatic lines and pneumatic connections thereby reducingfailure modes. The air dryer reservoir module 10 is thought to be thefirst of its kind to utilize the ABS/EBS brake system ECU to communicatesystem failures to the engine ECU to instruct the engine to limitvehicle speed. The, air dryer reservoir module 10 concept eliminates thesupply tank 60 thereby allowing the primary and secondary service tanks12 and 18 to communicate directly with the integrated air dryer 14through protection valves 35 and 36. This allows the protection valves35, 36 to be integrated into the air dryer module 10, reducing externalcomponents and pneumatic lines.

[0022] Referring now to FIGS. 4 and 5, the air dryer reservoir module 10operates as follows. Charge air from the air compressor 20 enters theair dryer reservoir module 10 at its supply port 31, flows through apurge valve 32 to the desiccant bed 33, fills the purge volume 34, flowsthrough a purge orifice (not shown) and flows out a single check valve(not shown). This represents the same charge cycle as used in anAlliedSignal AD 9 or AD IP air dryer. From the delivery of the singlecheck valve the charge air flows to the supply of the primary protectionvalve 35 and secondary protection valve 36. Charge air pressure buildsuntil the protection valves 35, 36 open, allowing air to flow to theprimary reservoir 18 and the secondary reservoir 12. Charge air pressurecontinues to build until the pressure sensors 37 or a mechanicalgovernor (not shown) reach cutout pressure. At cutout pressure the threeway solenoid 39 or the mechanical governor opens, sending a controlsignal through compressor unloader port 40, unloading the compressor 20and opening the purge valve 32 purging the air dryer 14. The purge cycleis the same as that of the AlliedSignal AD 9 or AD IP air dryer. The airdryer reservoir module's 10 integrated component configuration makes itcompatible with both integral purge and system purge type air dryeroperation and both mechanical and electrical type governors. This allowsa single dual function electric solenoid to control the air compressor20 unloading function and to purge the air dryer 14 using both theprimary and secondary service reservoirs 18 and 12 respectively. Thisconfiguration also allows both reservoirs 12, 18 to purge simultaneouslythereby reducing the total system pressure drop required to regeneratethe desiccant bed 33 with system purge type air dryer operation. Use ofpressure protection valves 35 and 36 instead of single check valves 66and 64 reduces compressor 20 cycling. Without the use of check valves 64and 66 primary reservoir 18 and secondary reservoir 12 are common atpressures above the protection valves 35, 36 opening pressure.Therefore, pressure differentials do not develop between primaryreservoir 18 and secondary reservoir 12 as air is consumed. Pressuredifferentials can develop in standard three reservoir system due toimproperly sized reservoirs and use of accessory systems, causing thecompressor to cut in before the air pressures in both reservoirs 12, 18have dropped to the cutin pressure.

[0023] The air dryer reservoir module 10 can be designed to utilizeservice reservoir air to purge the desiccant, i.e., supply purge. Theoperation of the air dryer reservoir module 10 in a supply purge modewill be similar to that of an AlliedSignal AD SP air dryer. The integralpressure protection valves 35, 36 will eliminate the need for externallyplumbed protection valves. The internal protection valves 35 and 36,when open will allow air to flow back to a special two position threeway system purge solenoid, located where the three way solenoid 39 is inthe integral purge design. The special two position three way systempurge solenoid will be controlled by the EBS ECU with inputs from thepressure sensors 37 through sensors/solenoid I/O 44. The system purgesolenoid will be designed to communicate a control signal to thecompressor 20 unloader and the air dryer purge valve 32 independently.At cutout pressure the system purge solenoid will unload the compressorand open the purge valve 32. The system purge solenoid will then closeonly the purge valve 32 after a predetermined amount of system air isused to purge the dryer's desiccant bed 33. At cutin pressure the systempurge solenoid will then load the compressor 20 starting the cycle over.

[0024] Referring now to Figures 6 and 6A, the embodiment of theillustrated air dryer reservoir module 10 operates as follows. Chargeair from the air compressor 20 enters the air dryer reservoir module 10at its supply port 31, fills the purge volume 34, and flows out a singlecheck valve 13. Check valve isolates the primary reservoir 18 and thesecondary reservoir 12 from the output of air dryer 14. An over pressuresafety valve 21 which is set for 150 psi is disposed at the outlet fromair dryer 14. From the delivery of the single check valve 13 the chargeair flows to the supply of the primary protection valve 35 and secondaryprotection valve 36. Charge air pressure builds until the protectionvalves 35, 36 open, allowing air to flow to the primary reservoir 18 andthe secondary reservoir 12. Charge air pressure continues to build atthe outlet of check valve 13 until a mechanical governor 15, which isconnected to the outlet of check valve 13, reach cutout pressure. Atcutout pressure, which is set at 130 ± 5 psi, the mechanical governor 15opens, providing a pressure drop signal through line 19, unloading thecompressor 20 and providing a pneumatic signal along line 17 forinitiating purging of the air dryer 14 with the compressed air containedin purge volume 34. Compressor 20 remains unloaded until the pressure togovernor 15 falls below the cutin pressure, which is set at 105 psi. Atthe cutin pressure the governor 15 closes and the compressor is loadedto again supply compressed air to the inlet 31 of air dryer 14.

[0025] The primary protection valve 35 is set to open at 103 ± 3 psi andto close at approximately 95 psi. The secondary protection valve 36 isset to open at 109 ±3 psi and to close at approximately 100 psi. Whenboth protection valve 35 and 36 are open the primary reservoir 18 andthe secondary reservoir 12 are in free fluid communication. Secondaryreservoir 12 provides compressed air to a vehicle leveling supply portthrough an accessory protection valve 41 which is set to open at 85 ± 3psi and to close at approximately 72 to 83 psi. Secondary reservoir 12also provides compressed air to vehicle accessories through an accessoryprotection valve 43 which is set to open at 55 ±3 psi and to close atapproximately 45 to 55 psi.

[0026] The air dryer reservoir module 10 is designed to accommodate therequirements of both FMVSS 121 and EEC regulation No. 13. The air dryerreservoir module 10 is also designed to interact with the ABS/EBSsystem's J1939/J1922 engine serial link to allow the limiting of vehiclespeed in the event of a single circuit brake system failure, eitherprimary or secondary. The air dryer reservoir module 10 reduces thenumber of OEM installed charging sub-system components, pneumatic linesand connections as follows: Major charging system components - four forair dryer reservoir module 10 vs. thirteen for a three reservoir system;pneumatic lines - three for air dryer reservoir module 10 vs. six for athree reservoir system; and pneumatic connections - thirteen for airdryer reservoir module 10 vs. thirty two for a three reservoir system.

[0027]Figure 5 shows the air dryer reservoir module in a completeservice brake system. The air dryer reservoir module 10 system can bedesigned to communicate pneumatic circuit failures through the ABS/EBSECU 50 to the engine serial link (J1922/JI939) to instruct the engine togo into a "limp" mode. The intention of this feature is to provide a"nuisance" motivator to the operator to have the vehicle repaired. Thesystem operates as follows: In the event of a failure of a pneumaticsystem which is supplied by either the primary reservoir 18 or thesecondary reservoir 12 the air dryer reservoir module's 10 integralpressure sensors 37 communicates the system pressure status to theABS/EBS ECU 50. The ECU 50 instructs the engine control module (ECM) 52to limit vehicle speed if the vehicle is in excessive of a set limit.

[0028] Referring now to Figure 4 there is shown the secondary reservoir12 with an integral purge volume 34. A baffle 53 separates the purgevolume 34 from the secondary reservoir 12. An internal tube 54 extendsthrough the purge volume 34 to connect the reservoir 12 throughconnections within housing 16 to the air dryer 14. A connection 55connects the purge volume 34 through connections within housing 15 tothe air dryer 14. This construction eliminates external lines forconnecting the air dryer 14 to the purge volume 34 and the secondaryreservoir 12. External lines have the potential for leak points, andcreate customer handling and mounting concerns. Building the purgevolume 34 required for the air dryer into the secondary reservoir 12allows the use of a compact system purge air dryer desiccant cartridgeand this minimizes the space required. Baffle 53 has tube 54 attachedthrough it and the tube 54 extends through the purge volume 34 andterminates at the head of the reservoir. The head of the reservoir hasattached to it the housing 16 which is integral with air dryer 14. Theair dryer communicates with both volumes 12 and 34 via separate passages54 and 55.

[0029] With a leaking reservoir 12 or 18 the dryer reservoir module 10described above will recharge the surviving reservoir indefinitely,thereby holding off the spring brakes. The driver can choose to operatethe vehicle with limited braking efficiency for an unlimited period oftime even though one of the reservoirs does not hold pressure. Inanother embodiment the dryer reservoir module 10 can be constructed toequalize the pressure between the reservoirs 12 and 18, such that if thevehicle is parked for a given period of time the pressure cannot bereplenished thereby limiting the use of the vehicle with a severelyleaking reservoir.

[0030] As shown in Figure 6 and described above, pressure protectionvalves 35 and 36 are used to supply compressed air to the primaryreservoir 18 and the secondary reservoir 12. The pressure protectionvalves 35, 36 are set to pressurize the primary reservoir 18 first,provided the same pressure exists within the primary and secondaryreservoirs. At full system pressure the pressure protection valves 35,36 are open, insuring equal pressure in both the primary and secondaryreservoirs 18 and 12. However, the pressure protection valve openingpressure is dependent upon the downstream reservoir pressure, therefore,if the reservoir pressures are not equal the pressure protection valvewhich has the highest downstream pressure will open first. Parking thevehicle overnight or for extended periods of time may cause the primaryand secondary reservoir pressures to become unequal. During rechargingof the air system the secondary reservoir 12 may charge before theprimary reservoir 18. It may be desirable to limit the duration thevehicle can be operated in the condition where one reservoir hassignificantly reduced pressure. By using a pressure equalizingmechanism, such as a connecting line with a suitable orifice 57, thepressures in the reservoirs 12 and 18 slowly become equal so that duringrecharging of the air system the primary reservoir 18 will charge first.Furthermore, if the primary reservoir 18 has become ruptured or has asevered leak, again the pressure in both reservoirs 18 and 18 willmigrate to 0 psi; however, the primary reservoir 18 can be recharged,but the essential accessories and air suspension will not be pressurizedbecause the secondary reservoir 12 cannot be recharged. The pressureequalizing mechanism 57 will cause the pressure in both reservoirs 12and 18 to be equal, thereby charging the primary reservoir 18 first andlimiting the use of the vehicle after a severe leak in either theprimary or secondary reservoirs 18 and 12.

What is Claimed is:
 1. An air dryer module, comprising: a housing; anair dryer mounted to the housing; a purge reservoir mounted to thehousing and communicating with the air dryer; and a port in said housingfor communicating dried air from the air dryer to a service reservoir, afirst portion of dried air passing from the air dryer to the purgereservoir, a second portion of the dried air passing from the air dryerto the service reservoir, and the first portion of the dried air notcommingling with the second portion of the dried air.
 2. The air dryermodule as set forth in claim 1, further including: a valve forcontrolling passage of the second portion of the dried air between theair dryer and the service reservoir.
 3. The air dryer module as setforth in claim 2, wherein the valve is a protection valve.
 4. The airdryer module as set forth in claim 2, wherein the valve is a checkvalve.
 5. The air dryer module as set forth in claim 1, wherein thefirst portion of the dried air passes from the purge reservoir to theair dryer for regenerating a desiccant in the air dryer.
 6. The airdryer module as set forth in claim 1, wherein the service reservoir islocated remote from the housing.
 7. The air dryer module as set forth inclaim 6, wherein the service reservoir is located remote from the purgereservoir.
 8. The air dryer module as set forth in claim 1, wherein: theair dryer is mounted to a first side of the housing; and the purgereservoir is mounted to a second side of the housing.
 9. The air dryermodule as set forth in claim 1, wherein the purge reservoir isindependent of the air dryer.
 10. The air dryer module as set forth inclaim 1, wherein the first portion of the dried air passes from the airdryer to the purge reservoir before the second portion of the dried airpasses from the air dryer to the service reservoir.
 11. An air dryermodule, comprising: a housing; an air dryer mounted to the housing; anda purge volume mounted to the housing and in fluid communication withthe air dryer via the housing.
 12. The air dryer module as set forth inclaim 11, further comprising: a first port in the housing for passing afirst portion of dried air between the air dryer and the purge volume;and a second port in the housing for passing a second portion of thedried air between the air dryer and a service reservoir, the first portbeing independent from the second port.
 13. The air dryer module as setforth in claim 12, wherein a first portion of dried air passes from theair dryer to the purge reservoir before a second portion of the driedair passes from the air dryer to the service reservoir, the firstportion of the dried air being different from the second portion of thedried air.
 14. The air dryer module as set forth in claim 12, wherein: afirst portion of dried air passes from the air dryer to the purgereservoir; a second portion of the dried air passes from the air dryerto the service reservoir; and the first portion of the dried air isdifferent from the second portion of the dried air.
 15. The air dryermodule as set forth in claim 12, wherein the first and second portsinclude respective connections.
 16. The air dryer module as set forth inclaim 12, wherein the purge reservoir is independent from the air dryer.17. The air dryer module as set forth in claim 11, wherein: the airdryer is mounted to a first side of the housing; and the purge volume ismounted to a second side of the housing.
 18. An air dryer module for useon a vehicle, comprising: a housing; an air dryer mounted to thehousing; a purge volume mounted to the housing and in fluidcommunication with the air dryer via the housing; and a first port insaid housing for communicating dried air from the air dryer to a purgevolume, a second port in said housing for communicating dried air fromthe air dryer to a service volume, a first portion of the dried airpassing between the air dryer and the purge volume via the first port, asecond portion of the dried air passing between the air dryer and theservice volume via the second port, the first port being independentfrom the second port.
 19. The air dryer module as set forth in claim 18,wherein the first and second ports include respective connections. 20.The air dryer module as set forth in claim 18, wherein the first portionof the dried air is independent from the second portion of the driedair.
 21. The air dryer module as set forth in claim 18, wherein thefirst portion of the dried air passes between the air dryer and thepurge volume before the second portion of the dried air passes betweenthe air dryer and the service volume.
 22. The air dryer module as setforth in claim 18, further including: means for controlling passage ofthe second portion of the dried air.
 23. The air dryer module as setforth in claim 22, wherein the means for controlling includes aprotection valve.
 24. The air dryer module as set forth in claim 22,wherein the means for controlling includes a purge valve.
 25. The airdryer module as set forth in claim 18, further including: means forcontrolling passage of the first portion of the dried air, wherein themeans for controlling purges the air dryer by causing the first portionof the dried air to pass from the purge volume to the air dryer.
 26. Theair dryer module as set forth in claim 25, wherein the means forcontrolling includes a purge valve.
 27. The air dryer module as setforth in claim 25, wherein the service volume is located remote from thepurge volume.
 28. The air dryer module as set forth in claim 27, whereinthe service volume is located remote from the air dryer.
 29. A methodfor charging an air brake system and regenerating an air dryer, themethod comprising: providing a housing having a first side and a secondside, an air dryer being mounted on the first side and a purge chamberbeing mounted on the second side; passing first dried air from the airdryer to the purge chamber via a first passage in the housing; passingsecond dried air from the air dryer to a service chamber, which is influid communication with the air dryer, via a second passage in thehousing communicating with the air dryer and the service chamber, thefirst dried air not being commingled with the second dried air; andpassing the first dried air from the purge chamber to the air dryer viathe first passage.
 30. The method for charging an air brake system andregenerating an air dryer as set forth in claim 29, wherein the step ofpassing the second dried air includes: passing the second dried airthrough a protection valve.
 31. The method for charging an air brakesystem and regenerating an air dryer as set forth in claim 29, furtherincluding: causing the first dried air to pass from the purge chamber tothe air dryer.
 32. The method for charging an air brake system andregenerating an air dryer as set forth in claim 31, wherein the causingthe first dried air to pass from the purge chamber to the air dryerincludes: passing the first dried air through a desiccant in the airdryer.
 33. A compressed air reservoir, comprising: a purge chamber; aservice chamber; a baffle defining the purge and service chambers; afirst passageway for transmitting first dried compressed air between adryer and the purge chamber; and a second passageway for transmittingsecond dried compressed air between the dryer and the service chamber,the first dried compressed air being transmitted between the dryer andthe purge chamber before the second dried compressed air is transmittedbetween the dryer and the service chamber.
 34. The compressed airreservoir as set forth in claim 33, further including: a valve, whichcontrols passage of the second dried compressed air between the dryerand the service chamber via the second passageway.
 35. The compressedair reservoir as set forth in claim 34, wherein the valve is aprotection valve.
 36. The compressed air reservoir as set forth in claim33, wherein the first dried compressed air in the purge chamber istransmitted to the dryer via the first passageway for regenerating adesiccant in the dryer.
 37. The compressed air reservoir as set forth inclaim 33, wherein the second passageway is a tube between the dryer andthe service chamber.
 38. The compressed air reservoir as set forth inclaim 37, wherein the tube passes through the purge chamber.
 39. Thecompressed air reservoir as set forth in claim 33, wherein a volume ofthe purge chamber is smaller than a volume of the service chamber.
 40. Amethod for storing compressed air in a compressed air reservoir, themethod comprising: providing the compressed air reservoir including apurge chamber in fluid communication with an air dryer, a servicechamber in fluid communication with the air dryer, and a baffle definingthe purge and service chambers; pressurizing the purge chamber withfirst dried compressed air from the air dryer; and after the purgechamber is pressurized with the first dried compressed air, pressurizingthe service chamber with second dried compressed air from the air dryer.41. The method for storing compressed air as set forth in claim 40,further comprising: depressurizing the purge chamber to regenerate theair dryer.
 42. The method for storing compressed air as set forth inclaim 41, wherein depressurizing the purge chamber includes:transmitting the first dried compressed air from the purge chamber tothe air dryer without commingling the first dried air and the seconddried air.
 43. The method for storing compressed air as set forth inclaim 40, wherein pressurizing the service chamber includes: controllinga valve between the service chamber and the air dryer.
 44. The methodfor storing compressed air as set forth in claim 40, further including:depressurizing the service chamber to operate a compressed air system.45. A compressed air reservoir, comprising: a purge chamber; a servicechamber; a baffle defining the purge and service chambers; a firstpassageway for transmitting purge air between an air dryer and the purgechamber; and a second passageway for transmitting service air betweenthe air dryer and the service chamber, the purge air being dryer thanthe service air.
 46. The compressed air reservoir as set forth in claim45 wherein the purge air is transmitted from the purge chamber to theair dryer for regenerating a drying agent in the air dryer.
 47. Thecompressed air reservoir as set forth in claim 45 wherein the purge airis transmitted to the purge chamber before the service air istransmitted to the service chamber.
 48. The compressed air reservoir asset forth in claim 45 wherein a volume of the purge chamber is smallerthan a volume of the service chamber.
 49. The compressed air reservoiras set forth in claim 45 further including: a valve which controlspassage of the service air between the dryer and the service chamber viathe second passageway.
 50. The compressed air reservoir as set forth inclaim 49 wherein the valve is one of a check valve and a pressureprotection valve.
 51. The compressed air reservoir as set forth in claim45 further including: a valve for directing the dryer air to the purgechamber.
 52. The compressed air reservoir as set forth in claim 51wherein the valve is associated with the first and second passageways.53. A compressed air reservoir, comprising: a purge chamber; a servicechamber; a baffle defining the purge and service chambers; a firstpassageway for transmitting purge air between an air dryer and the purgechamber; and a second passageway for transmitting service air betweenthe air dryer and the service chamber, the purge air being stored in thepurge chamber before the service air is stored in the service chamber,the purge air stored in the purge chamber being used for at least one ofregenerating an associated air dryer and supplying air to the servicechamber.
 54. A compressed air reservoir, comprising: a purge chamber; aservice chamber; a baffle defining the purge and service chambers; afirst passageway for transmitting purge air between an air dryer and thepurge chamber; and a second passageway for transmitting service airbetween the air dryer and the service chamber, the purge airpressurizing the purge chamber to a pressure for purging an associatedair dryer before the service chamber is pressurized with the serviceair.
 55. A compressed air system, comprising: a compressor for supplyingcompressed air; an air dryer connected to receive compressed air fromthe air compressor, the dryer including a drying agent through which thecompressed air flows for providing a dry compressed air source; and areservoir including: a purge section storing a purge portion of the drycompressed air; and a service section for storing a service portion ofthe dry compressed air, the purge portion of the dry compressed airbeing dryer than the service portion of the dry compressed air.
 56. Thecompressed air system as set forth in claim 55 further including: asecond reservoir, the service portion of the dry compressed air beingstored in both the service section and the second reservoir; whereinduring a first operating mode: the purge and service portions of thedried compressed air are transmitted from the dryer to the purge andservice sections, respectively; and if a pressure in one of the servicesection and the second reservoir is below a predetermined level, thepurge air is available to be transmitted from the purge section to theother of the service section and the second reservoir.
 57. Thecompressed air system as set forth in claim 56 further including: afirst protection valve set as a function of the pressure in the serviceportion; and a second protection valve set as a function of the pressurein the second reservoir; wherein if the pressure in one of the servicesection and the second reservoir is below the predetermined level, thepurge air is available to be transmitted from the purge section to theother of the service section and the second reservoir via the respectivefirst and second protection valve.
 58. The compressed air system as setforth in claim 56 wherein during a second operating mode: the purgeportion of the dried compressed air is transmitted from the purgesection to the air dryer for regenerating the drying agent.
 59. Thecompressed air system as set forth in claim 55 wherein: during one of aplurality of operating modes, the purge portion of the dried compressedair is transmitted from the purge section to the drying agent.
 60. Thecompressed air system as set forth in claim 59 wherein: during anotherof the operating modes, the purge and service portions of the driedcompressed air are transmitted from the dryer to the purge and servicesections.
 61. A compressed air system, comprising: a source ofcompressed air; an air dryer connected to receive the compressed air;and a reservoir including: a purge volume storing a purge portion of thedry compressed air received from the dryer; and a service volume forstoring a service portion of the dry compressed air received from thedryer, the purge volume being in a fluid path between the air dryer andthe service volume, and the purge portion of the dry compressed airincluding the driest compressed air for regenerating the dryer.
 62. Thecompressed air system as set forth in claim 61 wherein during one of aplurality of operating modes, the dry compressed air is transmitted fromthe dryer to the purge and service volumes.
 63. The compressed airsystem as set forth in claim 62 wherein during the operating mode, thedry compressed air is available to be transmitted from the purge volumeto the service volume if a pressure in the service volume is below apredetermined level.
 64. The compressed air system as set forth in claim62 wherein during another one of the operating modes, the dry compressedair is transmitted from the purge volume to the air dryer.
 65. Thecompressed air system as set forth in claim 64 wherein during the otherone of the operating modes, the dry compressed air is transmittedthrough a drying agent in the air dryer for regenerating the dryingagent.
 66. The compressed air system as set forth in claim 61 wherein avolume of the service volume is greater than a volume of the purgevolume.
 67. The compressed air system as set forth in claim 61 furtherincluding: another reservoir for storing a part of the service portionof the dry compressed air received from the dryer, the purge volumebeing in a fluid path between the air dryer and the other reservoir. 68.The compressed air system as set forth in claim 67 wherein if a pressurelevel of at least one of the service volume and the other reservoirdrops below a predetermined level, the purge portion of the drycompressed air is available to be transmitted to at least one of theservice volume and the other reservoir as an additional service portionof the dry compressed air.
 69. The compressed air system as set forth inclaim 61 wherein the purge portion of the dry compressed air is dryerthan the service portion of the dry compressed air.
 70. A method forcontrolling a compressed air system including a purge volume in fluidcommunication with an air dryer, a service volume in fluid communicationwith an air dryer, and a baffle defining the purge and service volumes,the purge volume being in a fluid path between the dryer and the servicevolume, the method comprising: pressurizing the purge volume with driedcompressed air from the dryer; and pressurizing the service volume withdried compressed air from the dryer, the air in the purge volume beingdrier than the air in the service volume.
 71. The method for controllinga compressed air system as set forth in claim 70 wherein the purgevolume is pressurized before the service volume.
 72. The method forcontrolling a compressed air system as set forth in claim 70 furtherincluding: if a pressure level in the service volume is below apredetermined level, making the dried compressed air in the purge volumeavailable to be transmitted to the service volume.
 73. The method forcontrolling a compressed air system as set forth in claim 70 wherein thecompressed air system also includes an additional reservoir in fluidcommunication with the air dryer, the purge volume being in the fluidpath between the dryer and the additional reservoir, the method furtherincluding: pressurizing the additional reservoir with dried compressedair from the dryer, the air in the purge volume being drier than the airin the additional reservoir.
 74. The method for controlling a compressedair system as set forth in claim 73 further including: if a pressurelevel in at least one of the service volume and the additional reservoiris below a predetermined level, making the dried compressed air in thepurge volume available to be transmitted to at least one of the servicevolume and the additional reservoir.
 75. The method for controlling acompressed air system as set forth in claim 70 further including:depressurizing the purge volume for regenerating the air dryer.
 76. Amethod for controlling a compressed air system including a purge volumein fluid communication with an air dryer, a service volume in fluidcommunication with an air dryer, and a baffle defining the purge andservice chambers, the method comprising: pressurizing the purge volumewith dried compressed air from the dryer; and after the purge volume ispressurized with the dried compressed air, pressurizing the servicevolume with dried compressed air from the dryer.
 77. The method forcontrolling a compressed air system as set forth in claim 76 whereinpressurizing the purge volume includes: transmitting the driest air fromthe dryer to the purge volume.
 78. The method for controlling acompressed air system as set forth in claim 76 further including:depressurizing the purge volume to regenerate the air dryer.
 79. Themethod for controlling a compressed air system as set forth in claim 76further including: if a pressure level of the service volume is below apredetermined level, depressurizing the purge volume for increasing thepressure level of the service volume.